(1) Field of the Invention
The present invention relates to a transmitting device, a receiving device, a system including these devices, and a method of transmitting digital data which is processed by animated image compression methods (frame encoding, animated compensation prediction) to a radio circuit at high efficiency.
(2) Description of the Related Art
Recently, various methods have been realized to process digital data of animated images. Generally, the information volume of an image is considerably large, so that it is necessary to compress/reduce the information volume before recording or reducing the image. For example, "ITU advice H. 261 video encoding method for audio visual service" is a method of encoding difference information between frames of an animated image.
In this encoding method or the like, the problem of transmission error is overcome by adding an error correction code to encoded image data. Also, a single frame of compressed data is transmitted at a certain interval so as to prevent the transfer of an error in difference information to succeeding frames.
However, when transmitting data by a radio line, the conventional encoding method has the following problem. Adding an error correction code to image data does not eliminate a burst error derived from a fading which is unique to a radio line. Originally, an error correction code was invented to overcome the problem of random error in a wire communication line.
Also, the addition of an error correction code increases the transmission amount, and this slows down the actual transmission rate.
Further, compared to the data amount taken to send difference information, the data amount taken to send one frame data is considerably large. Therefore, data transmission will be slow down at large. Especially when sending data at a low bit rate, the slow down of data transmission extends the time taken since the transmission starts until the reproduction ends (reproduction delay). Accordingly, scheduled smooth movements of animated images are interfered very badly.